“We visited the Mexico on our vacation last year.”

Why wrong: The definite article (“the”) is not used for streets, cities, provinces, states, countries, continents, mountains, islands, lakes or bays unless they are plural (the United States, the Alps or the Maritimes). When a country, state or province has a city that bears the same name, the word “City” is used afterwards (e.g. Mexico City, Panama City, Quebec City.) To be taken seriously…